Excelsior-Henderson Motorcycle Co. began producing motorcycles in the early 1900's. The early generation motorcycles included a front suspension system which incorporated a leading-link system. The leading-link system was based on a cantilever design where the axle of the front wheel was positioned in front of both rigid forks and spring forks. Although the system performed exceptionally well for motorcycles of that era, modern motorcycles are substantially larger and more powerful than their predecessors. As such, there is a need for an improved suspension and braking system compatible with today's motorcycle designs.
The performance of a motorcycle front suspension system is critical to both safety and operator comfort. With regard to safety, the front suspension system plays an important role in braking and steering. The front suspension system also contributes to rider comfort by absorbing shocks experienced during operation, and stabilizes the motorcycle during braking.
During braking operations, forward momentum of the motorcycle and its rider compress the front suspension. By compressing the front suspension during braking, the motorcycle rider experiences a diving sensation. To counteract this front end compression, the front suspension shock absorbing system can be adjusted to provide more compression damping, thereby resisting compression during braking. By increasing the stiffness of the front suspension, however, rider comfort is sacrificed during normal operation.
Different motorcycle front suspension systems have been described which attempt to reduce the amount of front end dive which is experienced during braking. For example, U.S. Pat. No. 4,775,163 issued Oct. 4, 1988 describes a motorcycle front suspension system which includes a leading link system having a rigid fork, a spring fork, and a rocker member. The rigid fork is attached to one end of the rocker member, and a front wheel axle is attached to an opposite end of the rocker member. The spring fork is attached to the rocker member at an intermediate location between the rigid fork and the spring fork. The suspension system also includes a brake caliper located in front of the spring fork and attached to both the front wheel axle and to the rigid fork through a link member. The patent describes the configuration as approximating a parallelogram having as its sides a segment of rigid fork, the rocker member, the brake caliper, and the link. It is asserted that when the front brake is applied and momentum drives the spring fork downward, the link induces a force up the rigid fork to increase the resistance of the suspension to retard "diving" of the motorcycle's front end.
U.S. Pat. No. 4,184,695 issued Jan. 22, 1980 also describes a motorcycle front fork assembly which includes a leading link suspension having a rigid fork, a spring suspension device and a link. Again, the rigid fork is attached to one end of the link and a front wheel axis is attached to an opposite end of the link. The spring suspension device is attached part way along the link between the rigid fork and the front wheel axis. A brake caliper is positioned in front of the spring suspension device and is attached to the rigid fork using a torque arm. The rigid fork, link, brake caliper and torque arm form a parallelogram. During braking, a force is exerted downward on the front wheel thereby reducing front end dive. The suspension systems described in the U.S. Pat. Nos. 4,184,695 and 4,775,163 place high stresses on the linkage components by locating the front wheel axis in front of both the rigid and spring forks. Further, these systems do not provide anti-dive characteristics through full suspension travel. That is, the suspension systems behave differently when the brakes are applied at different times during travel of the suspension.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a smoother suspension system which reduced component stress while reducing suspension compression due to braking operations.